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 fsdb_hfs(1M)							fsdb_hfs(1M)

      fsdb - HFS file system debugger

      /usr/sbin/fsdb [-F hfs] [-V] special [-b blocknum] [-]

      Always execute the fsck command (see fsck(1M)) after running fsdb.

      The fsdb command can be used to patch up a damaged file system after a

    Options and Arguments
      fsdb recognizes the following options and arguments.

	   special	  The file name of the special file containing the
			  file system.

	   -		  Initially disable the error-checking routines that
			  are used to verify the inode and fragment
			  addresses.  See the O symbol.	 If used, this
			  option must follow special on the command line.

	   -b blocknum	  Use blocknum as the superblock for the file
			  system.  If used, this option must follow special
			  on the command line.

	   -F hfs	  Specify the HFS file system type.

	   -V		  Echo the completed command line, but perform no
			  other action.	 The command line is generated by
			  incorporating the user-specified options and other
			  information derived from the /etc/fstab file.
			  This option allows the user to verify the command

      fsdb normally uses the first superblock for the file system, located
      at the beginning of the disk section, as the effective superblock.  An
      alternate superblock can always be found at block
      ((SBSIZE+BBSIZE)/DEV_BSIZE), typically block 16.	The -b option can be
      used to specify the superblock location.

      fsdb deals with the file system in terms of block fragments, which are
      the unit of addressing in the file system and the minimum unit of
      space allocation.	 To avoid possible confusion, fragment is used to
      mean that, and block is reserved for the larger true block.  fsdb has
      conversions to translate fragment numbers and i-numbers into their
      corresponding disk addresses.  Also included are mnemonic offsets to
      access different parts of an inode.  These greatly simplify the

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 fsdb_hfs(1M)							fsdb_hfs(1M)

      process of correcting control block entries or descending the file
      system tree.

      fsdb contains several error-checking routines to verify inode and
      fragment addresses.  These can be disabled if necessary by invoking
      fsdb with the optional - argument, or by using the O symbol.

      Numbers are considered decimal by default.  Octal numbers must be
      prefixed with a zero.  Hexadecimal numbers must be prefixed with 0x.
      During any assignment operation, numbers are checked for a possible
      truncation error due to a size mismatch between source and

      fsdb reads a fragment at a time.	A buffer management routine is used
      to retain commonly used fragments of data in order to reduce the
      number of read system calls.  All assignment operations result in an
      immediate write-through of the corresponding fragment.

      The following symbols are recognized by fsdb:

	   !	     Escape to shell
	   #	     Absolute address
	   +	     Address arithmetic
	   -	     Address arithmetic
	   <&lt&lt&lt;	     Restore an address
	   >&gt&gt&gt;	     Save an address
	   =	     Numerical assignment
	   =+	     Incremental assignment
	   =-	     Decremental assignment
	   ="	     Character string assignment
	   b	     Convert from fragment number to disk address
		     (historically "block")
	   d	     Directory slot offset
	   f	     File print facility
	   i	     Convert from i-number to inode address; for
		     continuation inodes as well as primary inodes (see
	   p	     General print facility
	   q	     Quit
	   B	     Byte mode
	   D	     Double-word mode
	   O	     Error checking flip-flop
	   W	     Word mode
	   X	     Hexadecimal flip-flop

      Dots, tabs, and spaces can be used as function delimiters, but are not
      necessary.  A line with just a newline character increments the
      current address by the size of the data type last printed.  That is,
      the address is set to the next byte, word, double word, directory
      entry, or inode, allowing the user to step through a region of a file

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 fsdb_hfs(1M)							fsdb_hfs(1M)


      Information is printed in a format appropriate to the data type.	If
      the X toggle is off, bytes, words, and double words are printed in the

	   octal-address  : octal-value	 (decimal-value)

      If the X toggle is on, bytes, words, and double words are printed in
      the form:

	   hex-address	: hex-value

      If the B (byte) or D (double-word) mode is in effect, the colon (:)
      shown above is preceded by .B or .D, respectively.

      Directories are printed as a directory slot offset followed by the
      decimal i-number and the character representation of the entry name.

      Inodes are printed with labeled fields describing each element.

    Print Facilities
      The print facilities generate a formatted output in various styles.
      Octal numbers are prefixed with a zero.  Hexadecimal numbers are
      prefixed with 0x.	 The current address is normalized to an appropriate
      boundary before printing begins.	It advances with the printing and is
      left at the address of the last item printed.  The output can be
      terminated at any time by typing the interrupt character.	 If a number
      follows the p symbol, that many entries are printed.  A check is made
      to detect fragment boundary overflows since logically sequential
      blocks are generally not physically sequential.  If a count of zero is
      used, all entries to the end of the current fragment are printed.	 The
      print options available are:

	   b	     Print as octal bytes
	   c	     Print as characters
	   d	     Print as directories
	   e	     Print as decimal words
	   i	     Print as inodes (primary or continuation)
	   o	     Print as octal words
	   x	     Print as hexadecimal words

      The f symbol prints data fragments associated with the current inode.
      If followed by a number, that fragment of the file is printed.
      (Fragments are numbered from zero).  The desired print option letter
      follows the fragment number, if present, or the f symbol.	 This print
      facility works for small as well as large files except for special
      files such as FIFOs, and device special files.

    Inode and Directory Mnemonics
      The following mnemonics are used for inode examination and refer to

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 fsdb_hfs(1M)							fsdb_hfs(1M)

      the current working inode:

	   anum	     Data block numbers (num is in the range 0 - 14)
	   at	     Time last accessed
	   ci	     Continuation inode number
	   ct	     Last time inode changed
	   gid	     Group ID number
	   ln	     Link count
	   maj	     Major device number
	   md	     Mode
	   min	     Minor device number
	   mt	     Time last modified
	   sz	     File size in byte unit
	   uid	     User ID number

      The following mnemonics are used for directory examination:

	   di	     I-number of the associated directory entry
	   nm	     Name of the associated directory entry

      386i	     Print i-number 386 in an inode format.  This now
		     becomes the current working inode.

      ln=4	     Change the link count for the working inode to 4.

      ln=+1	     Increment the link count by 1.

      fc	     Print in ASCII fragment zero of the file associated
		     with the working inode.

      2i.fd	     Print the first fragment-size piece of directory
		     entries for the root inode of this file system.

      d5i.fc	     Change the current inode to that associated with the
		     fifth directory entry (numbered from zero) found from
		     the above command.	 The first fragment's worth of bytes
		     of the file are then printed in ASCII.

      1b.px	     Print the first fragment of the superblock of this file
		     system in hexadecimal.

      2i.a0b.d7=3    Change the i-number for the seventh directory slot in
		     the root directory to 3.  This example also shows how
		     several operations can be combined on one command line.

		     Change the name field in the directory slot to the
		     given string.  Quotes are optional if the first
		     character of the name field is alphabetic.

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      a2b.p0d	     Print the third fragment of the current inode as
		     directory entries.

      Only experienced users should use fsdb.  The failure to fully
      understand the usage of fsdb and the file system's internal
      organization can lead to complete destruction of the file system and
      total loss of data.

      fsdb was developed by HP and AT&T.

      /etc/fstab     Static information about the file systems

      dumpfs(1M), fsck(1M), fsdb(1M), stat(2), dir(4), fs(4).

      fsdb: SVID3

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